1. Field of the Invention
The present invention relates generally to radio frequency identification (RFID) tags, and more specifically to RFID tags suitable for use in near and far range applications.
2. Discussion of the Related Art
A radio frequency identification (RFID) tag is an object that can be applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves. Some tags can be read from several meters away and beyond the line of sight of the reader. Most RFID tags contain at least two parts. One is an integrated circuit for storing and processing information, modulating and demodulating a radio-frequency (RF) signal, and other specialized functions. The second is an antenna for receiving and backscattering the signal. There are generally two types of RFID tags: active RFID tags, which contain a battery, and passive RFID tags, which have no battery. Today, RFID is used in enterprise supply chain management to improve the efficiency of inventory tracking and management.
Wal-Mart and the U.S. Department of Defense have published requirements that their vendors place RFID tags on all shipments to improve supply chain management. Typically, vendors use RFID printer/encoders to label cases and pallets that require electronic product code (EPC) tags. These smart labels are produced by embedding RFID inlays inside the label material, and then printing bar code and other visible information on the surface of the label.
However, vendors face significant difficulties implementing RFID systems. For example, the successful read rates currently run only 80%, due to radio wave attenuation caused by the products and packaging. That is, the RF characteristics and performance of a RFID UHF passive tag vary depending on the dielectric properties of the object it is placed on. Tag inlay manufacturers attempt designing tags that are the least effected by the object's dielectric. The dielectric of the item the tag is attached to changes the resonate frequency of the inlay's antenna. In order for the RF signal to get to the integrated circuit there has to be an impedance matching between the antenna and the chip. The more the antenna is detuned, the greater the impedance is mismatched. The tag's performance degrades as the impedance mismatch increases until the tag stops working.
Inlay manufacturers have had only moderate success at designing “universal tags” that will reliably function for all uses. The alternative is to design specific tags for specific types of product. As a further challenge, vendors will need to design tags that will meet tag certification which requires a particular tag be used for proper performance so that the tag can be read under many varying conditions through out the supply chain. This will lead to even more product specific tag designs.
Additionally, the manufacturers of consumer products will have to keep inventory of all the different tags that are required to sell their products. The right tag for a particular stock keeping unit (SKU) will have to be added to the Bill of Materials as a component and be managed through Materials Requirements. Planning (MRP). This adds one more link that can potentially stop the productions line for that SKU. There will be great pressure to substitute a different non-certified tag in order to keep the production line moving which will cause inventory inaccuracies down the supply chain. The burden to the supply chain both in cost and complexity creates a head wind that suppliers to retailers that require RFID tagging have to overcome.